Origin of prolific
Examples from the Web for prolifically
Arrogance begets fear as surely and prolifically as certain of the rodents beget offspring.The Conquest of Fear|Basil King
Corn grows as prolifically in Africa as in the bottoms of Georgia and Alabama.
He has taken some part in politics, but he continues to write, though not so prolifically as before.The Short-story|William Patterson Atkinson
Liberia would yield cotton as prolifically as Arkansas or Mississippi, if cultivated.